[PATCH 14/27] ext4: implement buffered read iomap path

Zhang Yi
2024-10-22T03:13:00Z

From: Zhang Yi <yi.zhang@huawei.com>

Introduce a new iomap_ops, ext4_iomap_buffered_read_ops to implement the
iomap read paths, specifically .read_folio() and .readahead() of
ext4_iomap_aops. This .iomap_begin() handle invokes ext4_map_blocks() to
query the extent mapping status of the read range and then converts the
mapping information to iomap.

Signed-off-by: Zhang Yi <yi.zhang@huawei.com>
---
fs/ext4/inode.c | 37 +++++++++++++++++++++++++++++++++++--
1 file changed, 35 insertions(+), 2 deletions(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index b233f36efefa..f0bc4b58ac4f 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3526,14 +3526,47 @@ const struct iomap_ops ext4_iomap_report_ops = {
.iomap_begin = ext4_iomap_begin_report,
};

-static int ext4_iomap_read_folio(struct file *file, struct folio *folio)
+static int ext4_iomap_buffered_read_begin(struct inode *inode, loff_t offset,
+ loff_t length, unsigned int flags, struct iomap *iomap,
+ struct iomap *srcmap)
{
+ int ret;
+ struct ext4_map_blocks map;
+ u8 blkbits = inode->i_blkbits;
+
+ if (unlikely(ext4_forced_shutdown(inode->i_sb)))
+ return -EIO;
+ if ((offset >> blkbits) > EXT4_MAX_LOGICAL_BLOCK)
+ return -EINVAL;
+ /* Inline data support is not yet available. */
+ if (WARN_ON_ONCE(ext4_has_inline_data(inode)))
+ return -ERANGE;
+
+ /* Calculate the first and last logical blocks respectively. */
+ map.m_lblk = offset >> blkbits;
+ map.m_len = min_t(loff_t, (offset + length - 1) >> blkbits,
+ EXT4_MAX_LOGICAL_BLOCK) - map.m_lblk + 1;
+
+ ret = ext4_map_blocks(NULL, inode, &map, 0);
+ if (ret < 0)
+ return ret;
+
+ ext4_set_iomap(inode, iomap, &map, offset, length, flags);
return 0;
}

-static void ext4_iomap_readahead(struct readahead_control *rac)
+const struct iomap_ops ext4_iomap_buffered_read_ops = {
+ .iomap_begin = ext4_iomap_buffered_read_begin,
+};
+
+static int ext4_iomap_read_folio(struct file *file, struct folio *folio)
{
+ return iomap_read_folio(folio, &ext4_iomap_buffered_read_ops);
+}

+static void ext4_iomap_readahead(struct readahead_control *rac)
+{
+ iomap_readahead(rac, &ext4_iomap_buffered_read_ops);
}

static int ext4_iomap_writepages(struct address_space *mapping,
--
2.46.1